Turbo-brushes are used, for example, for cleaning carpeted floors or the like, or for vacuuming carpets which have dirt ground into the carpet pile. German Patent DE 34 14 862 C2 describes a vacuum cleaner suction head having a wand connector, a glide sole, and a rotating brush roller. The brush roller is driven by a radial-inflow turbine. A relatively narrow, movable guide nozzle is disposed downstream of the turbine, said guide nozzle causing the suction air or primary air stream passing through the suction head to be concentrated onto the impeller or turbine wheel. The turbine is what is known as a drag-type device. Since the turbine is disposed in the primary air stream; i.e., operated with dirty suction air, it may happen that picked-up dirt particles clog the suction channel containing the guide nozzle or block the impeller. Such dirt accumulations must then be removed by the user of the turbo-brush. This is basically easy to do, but is nevertheless perceived as disagreeable.
Besides turbo-brushes having suction-air driven turbines, other turbo-brushes include reaction turbines which are disposed in a secondary air stream and driven by clean ambient air.
The main disadvantage of concepts using a turbine disposed in the primary air stream is the reduced efficiency, which is due to the fact that the dirt particles to be expected in the air stream make it impossible to work with the otherwise possible gap dimensions between the impeller and the turbine housing. Moreover, the blade spacing must be relatively large to allow dirt particles to pass through the impeller. Known reaction turbines which are operated with clean ambient air in the secondary air stream require the gap dimensions between the impeller and the turbine housing to be kept to a minimum in order to achieve sufficient efficiency. In addition, since the impeller speed is significantly (typically four times) higher compared to a drag-type device, a more complex conversion transmission is required to transmit the driving power to the brush roller.
GB 2 393 383 A describes embodiments of turbines including a radial-inflow turbine as well as a Pelton wheel.